How do catalysts affect the energy of reactions?
a. they absorb excess energy that would otherwise stop reactions from happening.
b. they act as low-energy materials that are used to make the products of the reactions.
c. they lower the activation energy required for the reactions to take place.
d. they act as fuel that burns and provides energy for the reactions.

Option (C) is the correct answer.

Explanation:

A catalyst is a substance which helps in increasing the rate of a chemical reaction by lowering the activation energy without itself getting consumed.

When reactant molecules does not have enough energy to cross the activation energy barrier then catalyst lowers the activation energy barrier. As a result, molecules with less energy are able to participate effectively that leads to increase in rate of reaction.

Hence, we can conclude that catalysts affect the energy of reactions as they lower the activation energy required for the reactions to take place.